Metal treatment – Stock – Ferrous
Patent
1994-06-29
1996-01-23
Yee, Deborah
Metal treatment
Stock
Ferrous
148603, 148661, 148651, C22C 3806, C21D 802
Patent
active
054862418
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to non-aging at room temperature ferritic single-phase cold-rolled steel sheet and hot-dip galvanized steel sheet for deep drawing and a process for producing the same.
The cold-rolled steel sheets and the hot-dip galvanized steel sheets according to the present invention are subjected to press molding before being used in automobiles, domestic electric appliances, buildings, etc. Since the steel sheets according to the present invention have a combination of strength with formability, the use thereof enables the sheet thickness to be reduced to a greater extent than that of the conventional steel sheets. In other words, a reduction in weight is possible. Therefore, the steel sheets of the present invention can be expected to contribute to environmental protection.
BACKGROUND ART
The production of an extra low carbon steel by a melt process has now become easy by virtue of advances in vacuum degassing processes for molten steels in recent years. This has led to an ever-increasing demand for extra low carbon steel sheets having a good fabricability.
It is well known that the extra low carbon steel sheet of this type generally contains at least one of Ti and Nb. Specifically, Ti and Nb interact with interstitial solid solution elements (C, N) in the steel, by a strong force of attraction, to easily form carbonitrides. Therefore, the resultant steel is a steel free from interstitial solid solution elements (IF steel: interstitial free steel). Since the IF steel does not contain an interstitial solid solution element causative of a deterioration in strain aging and formability, it has a feature that the formability in a non-aging state is very good. Further, addition of Ti and Nb plays an important role in improving deep drawability of the cold-rolled annealed steel sheet by virtue of grain refining of a hot-rolled sheet of an extra low carbon steel which is likely to coarsen. However, the extra low carbon steel containing Ti and Nb has the following problems. First, the production cost is high. Specifically, in addition to a vacuum treatment cost for rendering the carbon content extra low, addition of expensive Ti and Nb is necessary. Second, since neither C nor N in a solid solution form remains in the product sheet, fabrication embrittlement occurs or the paint-bake hardening disappears. Thirdly, Ti and Nb are powerful oxide forming elements, and the formed oxides deteriorate the surface quality.
Much research and development has hitherto been made with a view to solving the above problems of IF steel. For example, Japanese Unexamined Patent Publication (Kokai) Nos. 60-197846 and 63-72830 disclose extra low carbon steel sheets containing neither Ti nor Nb and process for producing the same, and fundamentally, the above problems are solved by the following technique. In continuously annealing a steel having a C content in the range of from 0.0010 to 0.0080%, high-temperature annealing is used to transform part of .alpha. to .gamma., and a low-temperature transformation product from .gamma. is then formed by regulating the cooling rate to provide a mixed structure comprising .alpha. and .gamma.. Since, however, the (.alpha.+.gamma.) two-phase region of the extra low carbon steel is very narrow, it is difficult to regulate the temperature with a high accuracy. In addition, there occur various problems associated with annealing at a high temperature, for example, a poor travelability of the sheet at a high temperature, a poor sheet configuration and a high energy consumption. For this reason, the steel sheet of the present invention comprises a structure with a single .alpha. phase. Further, Japanese Unexamined Patent Publication (Kokai) Nos. 59-80727, 60-103129 and 1-184251 and the like disclose cold-rolled steel sheets containing none of expensive elements such as Ti and Nb and having a C content including a region of not more than 0.0015% and a process for producing the same. In these steel sheets, however, the addition of B, which is one of the features of t
REFERENCES:
patent: 3827924 (1974-08-01), Takechi et al.
patent: 5078809 (1992-01-01), Kinoshita et al.
Akisue Osamu
Matsumura Yoshikazu
Murakami Hidekuni
Nishimura Kunio
Ushioda Kohsaku
Nippon Steel Corporation
Yee Deborah
LandOfFree
Non-aging at room temperature ferritic single-phase cold-rolled does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Non-aging at room temperature ferritic single-phase cold-rolled , we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Non-aging at room temperature ferritic single-phase cold-rolled will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-1502552